Complex Solid state thermal engines are devices that perform direct thermal-to-electric energy conversion without any moving parts. The solid state thermal engine is driven by hot sources, such as engine bleed air, wasted heat from operation of an electromechanical or thermal system, or some other heat source, such as the sun.
Solid state thermal engine technology is based on thermionics. Thermionics originated nearly a century ago with a basic vacuum tube, a device that consisted of two parallel conductive plates (a high temperature cathode and a low temperature anode) separated by a vacuum gap. During operation electrons boil off the cathode, traverse the gap and then are absorbed into the colder anode. The conversion of heat to electricity occurs as the electrons' kinetic energy results in a net current between the anode and cathode. These early vacuum gap designs have high manufacturing costs and high operating temperatures—above 1000° C., and require a very small gap for operation, on the order of hundreds of nanometers.
FIG. 1 illustrates an example solid state thermal engine that includes a cold electrode (B) and a hot electrode (A) separated by a gap. According to theoretical models, an alternative to conventional thermoionics is a device that relies on the effect of quantum mechanical tunneling which can occur between two electrodes, when the gap is between 1-10 nanometers. However, there are currently no devices that utilize a gap size in the one to ten nanometer range, for energy generation, even though there have been some claims in the literature to this effect.
Therefore, there exists an unmet need in the art to cost-effectively produce a solid state thermal engine that operates at much lower temperatures and at much higher efficiencies.